"Downton Abbey," the cultural juggernaut that offered the unwashed masses a glimpse into the staid yet dramatic life of early 20th-century English nobility, begins its final season in the United States on Sunday.

Created by Julian Fellowes, the show's sole writer, "Downton" premiered in 2010 on ITV in Britain and gained a foothold internationally, airing on PBS stations in America. It has been a ratings boon for PBS and ITV, even when viewers complained at points that it was beginning to lose steam.

The sixth and final season has already aired in Britain, with the finale drawing an average of 8.8 million viewers, its highest numbers since 2013.

The period drama follows the trials and tribulations of the aristocratic Crawley family and their servants on the Downton Abbey estate. Viewers quickly immersed themselves in trials affecting the family, including the death of a daughter, wartime losses and steamy affairs. Meanwhile, members of the servant class dealt with their own struggles around pregnancy, marriage and crime.

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Downton Abbey Creator Julian Fellowes on final season

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Showrunners announced in March 2015 that season six would be its last. Rumors of its impending end began swirling after Fellowes signed a deal to write "The Gilded Age," a period drama about New York high society for NBC.

Fellowes told CNN's Michael Smerconish the original intention was to end the show in season 5 until it became apparent "we had too much to do."

"We needed a whole series that was about resolution so we decided to do six, so it's not as if we're cutting ourselves short," he said.

"It's good to leave the party when the people are still sorry that you'll go and not wait until everyone's incredibly relieved."

The show began in pre-World War I England and reached the mid-1920s by the end of season 5. Season 6 picks up in 1925 with early reviews promising a few nods to the changing times with plenty of soap opera-style drama to boot.

The erosion of class lines and gender roles are persistent themes, Roslyn Sulcas wrote in The New York Times. Lady Edith (played by Laura Carmichael) and Lady Mary (played by Michelle Dockery) are working women while some of the servants branch out into other jobs.

Meanwhile, Robert (played by Hugh Bonneville) worries about the estate's finances while delays in a downstairs wedding kick up the sort of drama fans have come to expect from the series, Robert Bianco wrote in USA Today.

"For viewers and Abbey residents alike, impeccably performed surprises are in store, most infused with the sympathetic warmth that has helped the series survive a few bumps in its plotting."